Catalyst activators for use in polymerization of α-olefins are advantageous for use in a continuous solution polymerization process wherein catalyst, catalyst activator, and at least one polymerizable monomer are continuously added to a reactor operating under solution polymerization conditions, and polymerized product is continuously removed therefrom.
It is previously known in the art to activate single site or homogeneous (e.g., Ziegler-Natta) polymerization catalysts by the use of Bronsted acid salts capable of transferring a proton to form a cationic derivative of such Group 4 metal complex. Preferred Bronsted acid salts are such compounds containing a non-coordinating anion that is capable of stabilizing the resulting Group 4 metal cation, especially tetrakis(pentafluorophenyl)borate. Examples of such Bronsted acid salt activators, which are a species of ionic activator, are protonated ammonium, sulfonium, or phosphonium salts disclosed in, for example, U.S. Pat. Nos. 5,198,401, 5,132,380, 5,470,927, and 5,153,157.
Due to the fact that such activators are fully ionized, and the corresponding anion is highly non-coordinating, such activators are extremely effective as olefin polymerization catalyst activators. Disadvantageously, however, because they are ionic salts, such activators are extremely insoluble in aliphatic hydrocarbons, and only sparingly soluble in aromatic solvents. It is desirable to conduct most polymerizations of α-olefins in aliphatic hydrocarbon solvents due to the compatibility of such solvents with the monomer and in order to reduce the aromatic hydrocarbon content of the resulting polymer product. Normally, ionic salt activators need to be added to such polymerizations in the form of a solution in an aromatic solvent such as toluene. The use of even a small quantity of such an aromatic solvent for this purpose is undesirable since it must be removed in a devolatilization step and separated from other volatile components, a process that adds significant cost and complexity to any commercial process. In addition, the foregoing ionic cocatalysts often exist in the form of an oily, intractable material which is not readily handled and metered or precisely incorporated into the reaction mixture.
Highly soluble ammonium tetrakis(pentafluorophenyl)borate catalyst activator has been developed and successfully used in polyolefin production. Such activator is described in PCT Publication No. WO1997035893. Such highly soluble catalyst activator comprised a bis(hydrogenated tallowalkyl)methylamine derived from beef tallow. Due to increasing concerns over animal-derived material, and possible spread of Transmissible Spongiform Encephalopathies, there is a need to develop a highly soluble borate activator produced exclusively from non-animal-derived material. However, non-animal-derived high molecular weight tertiary amines that can be used as a direct replacement for the tertiary amine derived from beef tallow, currently, is not commercially available. Therefore, a method of making a tertiary amine for use in producing highly soluble catalyst activator, wherein the process does not utilize animal-derived products, is desirable.